As is well known to those of ordinary skill in the art, the performance of a metal pole thin film magnetic head structure is very sensitive to the final throat heights of the individual recording elements that make up that structure. As a result, during manufacture of the magnetic head structure, the throat heights of such recording elements must be carefully controlled. This is particularly critical in tape head structures since such structures include multiple recording elements aligned in a row, all of which must function properly for the tape head to function properly.
Such control of throat heights is generally accomplished using electrical lapping sensors which monitor throat heights during mechanical lapping of the tape head structure. Such sensors are typically fabricated in the tape head structure during the same thin film photolithographic process steps used to fabricate the recording elements themselves. Indeed, in prior art thin film tape head structures, the same metal layer and photolithographic process steps used to define the recording elements are also used to define the lapping sensor element. As a result, the lapping sensor provides a sufficiently accurate measure of the recording element throat heights, especially given the lower tolerances required for the throat heights of such prior art recording elements.
However, in newer thin film tape head structures, such throat height tolerances are tighter, and the electrical lapping sensors cannot be fabricated at the same time as the recording elements. In such structures, during thin film processing, the position of the "zero" throat is set by a baked photoresist "planar" insulating film layer, while the electrical lapping sensor is patterned in a metal film layer. The different photolithographic patterning steps between the lapping sensor and the photoresist planar introduces an alignment error. Depending on equipment and processing, this alignment error could vary anywhere from 0.5 up to 2.0 .mu.m.
Such newer thin film tape head structures, however, require recording element throat heights controlled to approximately 2.0 to 3.0 .mu.m, with tolerances of less than 0.5 .mu.m (10%-20%). As a result, there exists a need for an improved lapping sensor which provides a more accurate measure of the recording element throat heights during the mechanical lapping process. Ideally, such a sensor would still be manufacturable during the same thin film photolithographic process steps used to fabricate the recording elements themselves.